Specially formulated fluids are used during drilling and production of hydrocarbons to fulfill different functional requirements, conduct trouble free drilling and production operations, improve drilling efficiency and productivity of wells, and enhance the return on investment. Various types of fluids having different chemical compositions are used in such hydrocarbon drilling and production processes. For example, drilling and drill-in fluids, which are generally composed of a fluid phase, a chemical phase and a solid phase, are used while drilling for hole cleaning, borehole stabilization, cuttings suspension during non circulation, formation damage mitigation while drilling the reservoir section, and the like. As another example, fracturing and stimulating fluids, which are typically composed of a fluid phase, a chemical phase and a pseudo solid phase, are generally used to enhance the productivity of a field, especially a field with very low matrix permeability or a field that has incurred extensive formation damage while drilling.
Each of these fluids performs various functions during the drilling and production applications. For example, during drilling operations, drilling and/or drill-in fluids are circulated through the drill string to exit through the bit nozzles at high speed to remove the cuttings, clean the bit, transport the cuttings to the surface, prevent the fluid loss and particulate invasion to the reservoir, and the like. Similarly, during fracturing or stimulation operations of low permeable formations, a fracturing or stimulation fluid is pumped into the formation to improve the fluid flow characteristics of the field.
Conventional micro and/or macro particle-based fluids are commonly used in many drilling fluids because of their low manufacturing cost and availability in the market at a competitive price. For purposes of this application, the “micro” particle-based fluids generally have an average particle distribution of greater than about 1 micron. The “macro” particle-based fluids generally have an average particle distribution of equal to or greater than about 1 mm.
Although these conventional drilling fluids are effective in many applications, they have limited capability and may not be suitable for some current as well as some future drilling and production operations due to the increasingly challenging conditions of such operations. Many of the micro and/or macro particle-based drilling fluids have limited functional capabilities due to size effect; have low area to volume ratios; are difficult to manipulate to prepare tailored made particles with custom made properties, predominant role of physical and gravitational forces in the particle behavior; and have a lack of quantum effect due to trivial boundary effects.
Over the years, the operational conditions continue to become increasingly more extreme. For example, changes in the operational depth, nature of subsurface geo-hazards with increasing depth, length of horizontal departure to maximize production, complexity of drilling operation, shape of wellbore profiles or number of laterals from a mother bore to maximize reservoir contact, and the like all make drilling and production much more difficult. Moreover, the significant changes in the physical, chemical and thermal conditions of deeper horizons restrict the use of many conventional drilling fluids above a certain operational setpoint due to the limited physical, chemical, thermal and time dependant stability of many current fluids.
Because of the current limitations that exist using conventional drilling fluids, it is often impossible to fulfill certain functional tasks that are essential in challenging drilling and production environments using conventional macro and micro type fluid additives. A need exists for strong, stable, and customizable fluids to use virtually in all areas of oil and gas exploration and exploitation.
Nanoparticles have become increasingly popular in various polymeric compounds. Due to totally different and highly enhanced chemical, mechanical, electrical, physical, thermal, and hydrodynamic properties and interaction potential of nanomaterials compared to their parent materials, the nanoparticles are considered to be a promising material of choice for smart fluid design for oil and gas field applications. Moreover, due to the scope of manufacturing of tailored made nanomaterials with custom made functional behavior, ionic nature, physical shape and sizes, charge density/unit volume, nanotechnology is being used in the development of new drilling fluids defined as the smart fluids for drilling, production, and stimulation related applications.
Unfortunately, the formulation of viable drilling, drill-in, fracturing and stimulation fluids has been difficult using nanoparticles due to the active role of surface and molecular forces in the nanomaterial behavior. The solution to this problem in other industries has been to use a chemical dispersing agent, solvents, surfactants, and various other additives to prepare a viable nanofluid with homogeneous characteristics and long-term stability. Because the oil and gas industry uses huge quantity fluids to drill a well, the high cost of using expensive additives, such as chemical dispersing agents, in the preparation of nanofluids is not feasible for oil and gas field applications.
Drilling fluids are some of the biggest drilling and production costs associated with hydrocarbon recovery. Minimization of the cost factor associated with fluids, especially nano-based fluid is one of the major considerations in nanofluid formulation and preparation. Moreover, nanomaterials are also very costly on their own. The addition of another costly chemical as a dispersing agent could increase the cost of nano-based drilling fluids far beyond the industry acceptable economic norm. The industry needs a technically reliable and economically attractive method for preparation of a stable nano-based drilling fluid to meet the current as well as future technical challenges of the oil and gas industry.
Besides costs, other factors, such as the environmental impact of such drilling fluids, come into play when developing drilling fluids. Due to the enactment of increasingly strict environmental laws and regulations and setting of high environmental norms by environmental protection agencies, local, state or federal governments, environmental factor is another major consideration in oil and gas field applications due to the requirement of huge volume of nanofluids compared to other industries. The oil and gas industry needs an economically attractive and environmentally friendly fluid additive to prepare water-based nanofluids with a view to maintain the environmental friendliness of the fluid.